In a principal aspect the present invention relates to a tool for compressing the caliper pistons of a vehicle, dual piston disc brake assembly so that the disc pads may be removed and replaced. The invention thus comprises a manually actuated dual piston disc pad spreading tool.
In the repair of vehicles and, for example, with respect to the repair of vehicle braking systems, many special tools are desirable. Disc brakes thus may require special tools to facilitate repair. Disc brakes typically include a caliper housing which is mounted adjacent a wheel. The housing includes opposed disc pads which are piston driven toward one another for clamping a rotating disc associated with a rotating wheel of the vehicle to brake or stop the vehicle. From time to time, it is necessary to replace the pads due to the fact that they wear from frictional contact with the rotating disc. In such circumstances, the caliper housing is typically removed from the wheel assembly of the vehicle. The outboard pad is removed and the inboard disc pad mounted in the housing is caused to be spread apart by retracting the pad driving piston or pistons into the caliper housing. The pistons which have been pushed back allow adequate room for new pads to be replaced. The caliper housing may then be replaced in the wheel assembly and positioned for engagement with the brake disc.
Heretofore, applicant's assignee has made available in the marketplace a disc brake pad spreader tool, Lisle Product Model No. 24400. The Model No. 24400 disc brake pad spreader comprises a plate having a threaded rod through the center of the plate with a plunger mounted on the end of the rod. The plate is positioned against one side of a single-piston caliper brake pad frame, and the plunger is positioned against the inboard brake pad, so that by rotating the threaded bolt or rod, which connects the plate and plunger, the inboard pad is pushed back which forces the piston back into its cylinder.
More recently, applicant's assignee introduced an improved brake pad spreader tool, particularly designed for use with single piston disc brake constructions. The product, identified as Model No. 24300, is the subject matter of a separate patent application; U.S. patent application Ser. No. 10/339,091, filed Jan. 10, 2003, entitled Disc Brake Pad Spreading Tool, which is incorporated herewith by reference.
The described tools work quite well and have been widely accepted by auto mechanics responsible for the repair of disc brakes. A difficulty occurs with such tool designs; however, since the tools are not especially useful for repair of a dual piston disc brake assembly. This results because two separate, parallel drive, pistons mounted on the caliper housing are associated with such an assembly. That is, the pistons are mounted on a frame or housing wherein placement of a drive rod of the type in the above described tools is not possible because of the particular construction of the housing. The housing includes a center leg which interferes with positioning of the drive rod associated with the described tools.
Thus, there has developed a need for an improved disc brake pad spreading tool which can effectively retract the pistons mounted in the caliper housing for a dual piston disc brake and which can also compress simultaneously both of the pistons associated with the caliper housing.